repowering

[robymayway]

Hallo to all,
I 've got a 37 convertible with 2 dd 325 hp 671turbo , with shaft 1" 3/4 and propeller NI -BRA 4 blade 24 x 23
with cleaned hull they run at 16/17 knts at 2100 rpm and they have 2500 hours of life . I love my boat and I don't think to change boat in the next 5 years, so would like repower with two new engines.
I would like to increase with two MAN or CAT or CUMMINS around 450/480 hp
what do you suggest??what is the best?

Secondary, Shaft must be increased?
Also Have I to change propeller?

Are there some people that can help me?
Which are the steps?

thanks a lot
roberto - Italia

 

[ohiohatteras]

You are going to have to keep your boat waaaaaaaay longer than 5 years to even think about justifying a repower!

 

[newinlet]

I think the 671N motor for that boat is 310HP A turbo motor is 390 HP and some had 450 HP.

 

[robymayway]

Hallo,

Hatt 37 c is perfect for my life, correct size, correct affidability, perfect interior space for spent holiday with my family, perfectly easy to ordinary maintanence....but I love fishing and when I go fishing I have to run for around 60 miles + miles fishing + 60 miles to come back.


Run at 16/ 17 knt means 4/5 hour to go + 4/5 hour to come back + 6/8 hour for fishing at 7/8 knts.....is really too much time.

Also I have got a reserved place into my Marina, but the maximun size for my category is 13 metres..not a centimetre over. ( my hatt is 37 feet for 12,30 metre)

Considering also that CABO, Riviera, Bertram have pricing over my possibility, I have decided to repower my boat that is perfect and has everything I need to cruise with family ( I lived on board every week end of the year ) I have told 5 years just for my idea

I would like keep with my hatt for longer, but my dream would be run at 22 / 24 knt with a new safety affidability.......is it only a dream?????

thanks

roberto - Italia

 

[the kuz]

If you look at a repower as an investment that you want to recover, it's not going to happen. But if you like your boat and look at what it would cost for a new or nearly new alternative, then repower makes a lot of sense. We put about $100K into a 1977 36C four years ago and don't regret it for a minute (even though that may be more than we could get for the boat if sold today). New everything, from the battery boxes, instruments, and fuel lines out the exhausts, and of course two new deisels (B series Cummins) and a new genset (Northern Lights). Mechanically a brand new boat that went from a 15 -17 KNT to a comfortable 23 - 24 KNTS cruise using about 1/2 the GPH as with the old engines. Would cost many times what we spent to get a comparable "New" boat. So we have a "new boat" comfort level going anywhere and plan on keeping this boat a long time.

I'm partial to Cummins (C series or QSMs for your boat), you can make your props and shafts work with the right transmission ratio, but for what you are going to spend (unless you do it yourself) I would check into optimizing the entire package. It may be that what you have is right on or maybe not. Other threads here have discusssed shaft size - depends on what kind of shafts, and how much HP you plan on going with - my guess is your absolute max is about 450 HP on 1 3/4 shafts. Not sure about the high speed characteristics of your 37 hull - you need to check. Some Hat bottoms just don't want to go real fast. My series one 36C is stable up to about 28 -29 KNTS then starts to ride too high up on the keel and "walk" a little. Not a problem anymore now that we have so much stuff/weight on board that we top out at 28 KNTS.

If you like your boat, go for it and enjoy it. Just don't expect to get your "investment" back when you sell.

Regards, Bob K

 

[34Hatt]

If you look at a repower as an investment that you want to recover, it's not going to happen. But if you like your boat and look at what it would cost for a new or nearly new alternative, then repower makes a lot of sense. We put about $100K into a 1977 36C four years ago and don't regret it for a minute (even though that may be more than we could get for the boat if sold today). New everything, from the battery boxes, instruments, and fuel lines out the exhausts, and of course two new deisels (B series Cummins) and a new genset (Northern Lights). Mechanically a brand new boat that went from a 15 -17 KNT to a comfortable 23 - 24 KNTS cruise using about 1/2 the GPH as with the old engines. Would cost many times what we spent to get a comparable "New" boat. So we have a "new boat" comfort level going anywhere and plan on keeping this boat a long time.

I'm partial to Cummins (C series or QSMs for your boat), you can make your props and shafts work with the right transmission ratio, but for what you are going to spend (unless you do it yourself) I would check into optimizing the entire package. It may be that what you have is right on or maybe not. Other threads here have discusssed shaft size - depends on what kind of shafts, and how much HP you plan on going with - my guess is your absolute max is about 450 HP on 1 3/4 shafts. Not sure about the high speed characteristics of your 37 hull - you need to check. Some Hat bottoms just don't want to go real fast. My series one 36C is stable up to about 28 -29 KNTS then starts to ride too high up on the keel and "walk" a little. Not a problem anymore now that we have so much stuff/weight on board that we top out at 28 KNTS.

If you like your boat, go for it and enjoy it. Just don't expect to get your "investment" back when you sell.

Regards, Bob K

Being one that also did almost the same as Bob above I can't say it better then he just did.
I don't regreat doing mine and I don't plan on selling so I can't lose any money

 

[robymayway]

If you look at a repower as an investment that you want to recover, it's not going to happen. But if you like your boat and look at what it would cost for a new or nearly new alternative, then repower makes a lot of sense. We put about $100K into a 1977 36C four years ago and don't regret it for a minute (even though that may be more than we could get for the boat if sold today). New everything, from the battery boxes, instruments, and fuel lines out the exhausts, and of course two new deisels (B series Cummins) and a new genset (Northern Lights). Mechanically a brand new boat that went from a 15 -17 KNT to a comfortable 23 - 24 KNTS cruise using about 1/2 the GPH as with the old engines. Would cost many times what we spent to get a comparable "New" boat. So we have a "new boat" comfort level going anywhere and plan on keeping this boat a long time.

I'm partial to Cummins (C series or QSMs for your boat), you can make your props and shafts work with the right transmission ratio, but for what you are going to spend (unless you do it yourself) I would check into optimizing the entire package. It may be that what you have is right on or maybe not. Other threads here have discusssed shaft size - depends on what kind of shafts, and how much HP you plan on going with - my guess is your absolute max is about 450 HP on 1 3/4 shafts. Not sure about the high speed characteristics of your 37 hull - you need to check. Some Hat bottoms just don't want to go real fast. My series one 36C is stable up to about 28 -29 KNTS then starts to ride too high up on the keel and "walk" a little. Not a problem anymore now that we have so much stuff/weight on board that we top out at 28 KNTS.

If you like your boat, go for it and enjoy it. Just don't expect to get your "investment" back when you sell.

Regards, Bob K

Really tanks Bob,
First of all I have to say that I don't expect to get my investment back when I will sell.
I want refresh my boat only for myself.
Could you send some photos made during your job?
thanks
robyronch@libero.it

 

[41-Hatteras]

I repowered my 1966 41-C with 450 cummins & 1.5 ZF grears. used thesame size shafts but up graded, used the same props. 23x24 she runs 33 kts at 2600 rpm, cruzes at 26kts. I run her at 1800 rpms 19-21 kts 14 gal an hour. Just took her to Roatan Honduras from Galveston, 1080 KM, 92 hrs 1400 gal fuel.
Captn Ron

 

[REBrueckner]

Sounds like you want to run faster. Have you considered boosting your current engine HP with larger injectors as a compromise?

48 Hatt YF with 435 HP DD used 2" shafts; I believe the YF with naturals at 350 HP also used 2 inch shafts....Can anyone confirm that????...because you will be running offshore and running at higher speeds I'd NOT take ANY chance on shaft size....I'd suggest calling pros/manufacturers for a shaft size answer. And be sure to specify your shaft material Aquamet 22???? It would be unlikely you'd be able to use your current props, maybe a 1 in fifty chance they'd happen to be correct.

I'd be surprised if your 1.75" shafts would take over about 375 HP.....but that MIGHT depend on engine characteristics..just a guess.

Based on commercial installations I see in the NE, I'd go with CATS: I have never seen a MAN and only rarely Cummins.

But some engine models are for recreational applications and different versions for commercial application. There is now a $10,000 federal fine for installing recreational engines in commercial craft (I saw stickers on some new Yanmars and asked my mechanic) but I don't know if doing the opposite is permitted nor if you would want to do that.

 

[Brian Degulis]

Cummins QSL 9 is probably your best option. They produce around 405HP @2100 RPM on a medium continous rating. So on your boat you could run WOT all day every day and probably never wear them out. Or you could go to a recreational boat rating and come up to like 500 HP. They are about the same size as your 671s depending on what gears you have you might be able to use them and just change ratios or prop size.

Brian

 

[saltshaker]

How much room do you have in the engine room? That HP rating sounds like a 671 laydown or incline engine. Is your engine mounted lying on it's side? If so you may have some height restrictions that could limit your options. Newer engines with down angle gears might be OK. If you do have 671 laydowns, I would not put money into upgrading them. They don't work well in higher HP configurations and parts are harder to get and very expensive.

As far as what to use for your repower, go with what fits your needs and offers the best product support in your area. I like Brian's choice of the Cummins QSL 9, if you have the room. A friend of mine has a medium continuous rated Cummins in his boat. He put just under 2000 hours on it in 2 years. He just had the engine checked out by Cummins and it shows no real wear. If you don't have the space and want more speed, Cummins has a lot of different options for you. If the engines are rated at higher RPM's and you go with a lower reduction gear, say 1.5:1, you should find a power package in the 450HP range that would allow you to keep your shafts. Keep in mind your 37C is much heavier and has more beam than the older 36C and even the 41C. You will need more HP than those boats to achieve a 24kt cruise. I would think 450HP would be more than enough to do it but that is only a guess.

 

[Boatsb]

I would be taking the questions to a few local yards or engine suppliers to run numbers. We run the numbers for cummins repower people all the time. We have estimated and real world results from other repowers to confirm the results. If you look at the reults from previous repowers they did and find what you are looking for go that way.

 

[rwetherington]

i would be glad to hellp you run the number of different engines we have done quite a few repower with the cummins and cat. give me a call if you would like to talk about repowering

 

[robymayway]

How much room do you have in the engine room? That HP rating sounds like a 671 laydown or incline engine. Is your engine mounted lying on it's side? If so you may have some height restrictions that could limit your options. Newer engines with down angle gears might be OK. If you do have 671 laydowns, I would not put money into upgrading them. They don't work well in higher HP configurations and parts are harder to get and very expensive.

As far as what to use for your repower, go with what fits your needs and offers the best product support in your area. I like Brian's choice of the Cummins QSL 9, if you have the room. A friend of mine has a medium continuous rated Cummins in his boat. He put just under 2000 hours on it in 2 years. He just had the engine checked out by Cummins and it shows no real wear. If you don't have the space and want more speed, Cummins has a lot of different options for you. If the engines are rated at higher RPM's and you go with a lower reduction gear, say 1.5:1, you should find a power package in the 450HP range that would allow you to keep your shafts. Keep in mind your 37C is much heavier and has more beam than the older 36C and even the 41C. You will need more HP than those boats to achieve a 24kt cruise. I would think 450HP would be more than enough to do it but that is only a guess.

Unfortunatly in Italy thereisn't a good technical support from Cummins dealer, but assistance look great!!
Actually they are placed inclined and they are very big respect actually cummins or cat. I want leave DD because I agree with you : They don't work well in higher HP configurations and parts are harder to get and very expensive.
450 hp seems to be what I need, but I wouldn't change shaft or props...if possible

 

[robymayway]

I would be taking the questions to a few local yards or engine suppliers to run numbers. We run the numbers for cummins repower people all the time. We have estimated and real world results from other repowers to confirm the results. If you look at the reults from previous repowers they did and find what you are looking for go that way.

Yes, I agree with you...Cummins 450 hp seems to be a good compromise, but I am looking for find some previous "hatteras friends" that could help me to schedule the best job possible. I would like avoid to fall in some "expensive" surprise during my working in progress!!!

 

[robymayway]

Cummins QSL 9 is probably your best option. They produce around 405HP @2100 RPM on a medium continous rating. So on your boat you could run WOT all day every day and probably never wear them out. Or you could go to a recreational boat rating and come up to like 500 HP. They are about the same size as your 671s depending on what gears you have you might be able to use them and just change ratios or prop size.

Brian

can you suggest me a web adress to see them? Do you believe that I could keep my allison transmition with 1 3/4 shaft and actually props? have you some feedback about this??
really thanks
roberto - Italy

 

[robymayway]

I repowered my 1966 41-C with 450 cummins & 1.5 ZF grears. used thesame size shafts but up graded, used the same props. 23x24 she runs 33 kts at 2600 rpm, cruzes at 26kts. I run her at 1800 rpms 19-21 kts 14 gal an hour. Just took her to Roatan Honduras from Galveston, 1080 KM, 92 hrs 1400 gal fuel.
Captn Ron

Thanks Ron
did you get some photos? robyronch@libero.it
I would like your job steps.
which type of cummins you have installed?
Please give me a confirm if your shaft are actually 1 3/4 and prop23x24 as mine.
thanks a lot

 

[robymayway]

Sounds like you want to run faster. Have you considered boosting your current engine HP with larger injectors as a compromise?

48 Hatt YF with 435 HP DD used 2" shafts; I believe the YF with naturals at 350 HP also used 2 inch shafts....Can anyone confirm that????...because you will be running offshore and running at higher speeds I'd NOT take ANY chance on shaft size....I'd suggest calling pros/manufacturers for a shaft size answer. And be sure to specify your shaft material Aquamet 22???? It would be unlikely you'd be able to use your current props, maybe a 1 in fifty chance they'd happen to be correct.

I'd be surprised if your 1.75" shafts would take over about 375 HP.....but that MIGHT depend on engine characteristics..just a guess.

Based on commercial installations I see in the NE, I'd go with CATS: I have never seen a MAN and only rarely Cummins.

But some engine models are for recreational applications and different versions for commercial application. There is now a $10,000 federal fine for installing recreational engines in commercial craft (I saw stickers on some new Yanmars and asked my mechanic) but I don't know if doing the opposite is permitted nor if you would want to do that.

please, could you let me know some web adress to contact about shaft and props ?? I will contact for an opinion

 

[brian4190]

i recently repowered my series 2 36 (28,000lbs) from 6-71ti 410hp to cummins 450c remans. used 1.75:1 zf trans. the 450c's are 1,000lbs lighter each. used the same 1 3/4" shafts. i am very pleased with the results.

 

[robymayway]

i recently repowered my series 2 36 (28,000lbs) from 6-71ti 410hp to cummins 450c remans. used 1.75:1 zf trans. the 450c's are 1,000lbs lighter each. used the same 1 3/4" shafts. i am very pleased with the results.

have you some photos of your job?
which series of cummins you have installed ?
robyronch@libero.it

thanks roberto